青藏高原INDEPTH-Ⅲ剖面地壳厚度与泊松比：地质与地球物理含义

对INDEPTH Ⅲ台站的接收函数进行扫描，利用Moho界面产生的转换波和多次波的走时信息，估计台站下方的地壳平均波速比VP/VS和地壳厚度.结果显示：（1）沿着INDEPTH Ⅲ剖面，地壳厚度整体变化不大，均为65±5km，其中拉萨地块Moho界面埋深较羌塘地体要深约5～6km.结合其他研究资料，我们推断，在整个班公-怒江缝合带存在约10km的Moho错断，为拉萨地体北缘的地幔盖层向北俯冲到羌塘地体之下所致.（2）青藏高原地壳平均波速比整体都较高，可能与青藏高原地壳广泛存在的流体/部分熔融岩浆有关.拉萨地体北部异常高的地壳VP/VS可能与嘉黎-崩错右旋走滑断裂相关；而另一个泊松比异常区位于羌塘中北部（st36～st40），它可能是由热的地幔引起的壳内部分熔融所致.

The Poisson ratio and crustal structure of the central Qinghai-Xizang inferred from INDEPTH-Ⅲ teleseismic waveforms: Geological and geophysical implications

Teleseismic conversion and multiple waves recorded by the INDEPTH Ⅲ seismic array have been used to investigate the crustal thickness and VP/VS ratios of the central Qinghai_Xizang Plateau. Comparison with the crustal thicknesses obtained from other studies shows good agreement, which suggests that our measurements are reliable. Our results reveal that (1) the crustal thickness is 65±5km beneath the central Tibet. On the average, the Moho in Qiangtang is 5～6km shallower than that in Lhasa terrane. (2) A～10km Moho offset occur along the BNS, which maybe result from the northward subduction of the Lhasa mantle lid beneath the Qiangtang terrane affected by the India_Asia collision. (3) Due to extensive crustal melting/fluid beneath the central Qinghai_Xizang Plateau, the average crust Poission's ratios are high (025～032). The high Poission's ratio abnormality in the northern Lhasa may be related to the Bong Co_Lhari fault. Another high Poission's ratio abnormality located on the northern Qiangtang terrane (st36～st40) can be related to the crustal partial melting resulted from the high heat flux from abnormal upper mantle beneath the north central plateau.